The present invention relates to an apparatus for measuring three-dimensional curved surface shapes in a noncontact manner and more particularly to the compensation for distortions due to the perspective effect of its television camera.
Three-dimensional curved surface shape measuring apparatus have been proposed, for example, in U.S patent application Ser. No. 259,037. In these apparatus, the three-dimensional curved surface shape of an object to be measured is measured by scanning a linear slit light all over the surface of the object to form a composite image in which the value of each of the picture elements within the picture of a video signal produced by picking up the surface of the object is represented by information relating to the position of the slit light at the instant that the slit light passes one of the positions on the object surface corresponding to that picture element and subjecting the composite image to a computational processing.
However, this shape computing method is based on the tacit assumption that the distance between the television camera and an object to be measured, infinitely great or can be considered to be infinitely great. Where the distance between the television camera and the object to be measured is finite and the perspective effect cannot be ignored when observing the object from the television camera as in the actual measuring system, there is a disadvantage that if this shape computing method is applied as such, distortions due to the perspective effect are caused in the shape measurement result obtained.